DE102011005596A1 - Electronic ballast for operating at least one LED and / or at least one discharge lamp - Google Patents

Abstract

The present invention relates to an electronic ballast for operating at least one LED and / or at least one discharge lamp (FL). Such an electronic ballast has a control input (SW) for coupling in a control signal from a control device, for example a motion detector (10). To reduce interference voltages due to line capacitances of a control line (SL) coupled to the control input (SW), an additional capacitance (Cneu2) is provided, which forms a capacitive voltage divider with the line capacitance (Ck).

Description

Technical area

The present invention relates to an electronic ballast for operating at least one LED and / or at least one discharge lamp having a first connection for coupling to a phase of an AC supply, a second connection for coupling to the neutral of the AC supply, a control input for coupling a control signal of a control device, which is in turn coupled to a phase of the AC power supply, a first output for coupling to the at least one LED, a second output for coupling to the at least one discharge lamp, a first driver circuit for the at least one LED, a second driver circuit for the at least one discharge lamp, an evaluation device for evaluating the control signal at the control input, wherein the evaluation device comprises a microcontroller, which is coupled to the first and the second driver circuit, in response to the control signal to activate, wherein the microcontroller has a drive input, which is coupled to the control input.

State of the art

In conventional installations of lighting equipment in combination with a motion detector, as are known, for example from staircases in the prior art, coupled with the motion detector phase of an AC power supply to the motion detector downstream electronic ballast of the lighting device is coupled with activation of the motion. As a result, the lighting device is turned on.

In recent times, electronic ballasts have become known, for example, the so-called dual-power ECG of the Applicant, in which by means of a control input, a specific operating mode can be selected. In the case of the electronic ballast mentioned as an example, it is possible in this connection to operate only at least one LED or only at least one discharge lamp or both at the same time. In such an electronic ballast, the switching output of the motion detector is coupled to the control input of the electronic ballast, while the electronic ballast itself is coupled to a phase of the AC power supply. If there is no defined signal at the control input, an undesired signal at the control input, which is misinterpreted by the evaluation device, can result from capacitive coupling of other voltage-carrying lines. The danger of capacitive couplings exists in particular because the coupled to the control input control line, sitting at the other end of the motion detector is often laid parallel to the AC power supply line of the electronic ballast.

One known from the prior art in this. Interrelated evaluation device is shown schematically in FIG 1 shown. If a switch S1 is closed, a voltage drops across a shunt resistor R1 which is proportional to the voltage at the control input SW. A voltage divider is formed by the ohmic resistors R1 and R2, between which a diode D1 is coupled for the purpose of rectification. Two varistors Var1 and Var2 serve to protect the switch S1 against overvoltages. The distance switch S1 and ohmic resistance R1, the capacitor C1 is connected in parallel. The microcontroller μC queries the voltage drop across the shunt resistor R1 in a ratio of 1:10. Dis has its cause in that in the in 1 represented evaluation device, the input impedance is only 10 kOhm and can be minimized by the control in the ratio 1:10 losses of the evaluation device. In addition to the costs for the varistors Var1, Var2, the design of the switch S1 is problematic in the present case. This must be rated at 800 V with regard to surge pulses.

An increase of the input impedance to reduce the losses is out of the question as this would increase the problems due to capacitive charges on the control line. Namely, if the input impedance is increased, the discharge of the line capacitance would be slower and would therefore adversely affect the evaluation of the control signal SW at the input of the microcontroller μC. An increase in the duty cycle for the purpose of counteracting an increase in the input impedance, in turn, would result in an increase in the time portions in which current flows from the control input SW to the reference potential, whereby the losses of the evaluation device would be increased again. Moreover, it is disadvantageous that the evaluation device claims two pins of the microcontroller μC. There are applications in which only a single pin for the evaluation device can be provided.

Presentation of the invention

The object of the present invention is therefore to develop a generic electronic ballast such that an increased immunity to interference of the control input can be provided at the same time low cost.

This object is achieved by an electronic ballast having the features of claim 1.

The present invention is based on the finding that in the phase in which the control input a mains half-wave is applied (such states are hereinafter referred to as "ON"), the line capacitance is short-circuited and therefore a capacitive voltage divider, which acts on the control input line capacitance includes control line to be connected to the control input as well as the first capacity, does not work. The capacitive voltage divider acts only in the phase in which the signal at the control input is "OFF", that is zero. Exactly in the phase in which the disturbances occur due to the line capacitance, these are reduced by means of the capacitive voltage divider and thus reduce the risk of misinterpretation of the signal at the control input of the microcontroller.

Due to this measure, the interference immunity of the control input can be significantly increased. Thus, longer control lines can be connected to the electronic ballast, creating larger applications can be opened. Compared to the prior art, there is a significant cost savings, since no varistors are needed. Likewise, no switch needs to be sized to 800V. Due to this saving also results in a reduced space requirement.

A preferred embodiment of the present invention takes into account the fact that with the phase and the neutral conductor to which an electronic ballast according to the invention is coupled, in practice further lighting devices and electronic ballasts can be coupled, for example, all of them via one and the same motion detector - and turn off. However, if, for example, coupled between the coupled to the motion detector phase, which is to be coupled to the control input of an electronic ballast according to the invention, and the neutral conductor an incandescent lamp, it acts as an ohmic resistance. The signal on the neutral is transmitted in this way via the light bulb to the control input of an electronic ballast according to the invention and there disturbs the evaluation of the control signal. To prevent this, it is provided according to this preferred embodiment that the evaluation device further comprises a masking device which is coupled between the control input and the control input of the microcontroller, wherein the masking device is designed to supply the control signal to the control input of the microcontroller only during the time periods during which the signal at the second port is zero. Thus, in the periods in which there is a signal on the neutral, which could lead to disturbances, the control signal is not coupled to the control input of the microcontroller. Disturbances by other with the same control device, in particular motion detectors, coupled lighting devices can therefore be reliably avoided.

Preferably, such a masking device comprises an electronic switch having a control electrode, a reference electrode and a working electrode, wherein the control electrode is coupled to the second terminal, wherein the reference electrode is coupled to a reference potential, in particular ground, wherein the working electrode is coupled to a coupling point, which is coupled to the drive input of the microcontroller on the one hand and the control input on the other hand. Due to this constellation, with a signal ON on the neutral, the coupling point is pulled to ground, and thus the control input of the microcontroller. In the case of a signal OFF on the neutral, however, the electronic switch blocks so that the signal at the control input is applied via the coupling point to the control input of the microcontroller.

Further preferably, a second capacitance is coupled between the coupling point and the reference potential. This second capacitance serves to suppress disturbances caused by noise injections as a result of burst pulses.

Furthermore, a first ohmic resistance is coupled between the control input and the coupling point, and a second ohmic resistance is coupled between the control input of the microcontroller and the reference potential. This results in a voltage divider, which can be designed in the present constellation in contrast to the prior art high impedance. The losses due to the evaluation device are therefore minimal. The input impedance of the control input in the case of an electronic ballast according to the invention is preferably between 700 kOhm and 2 MOhm, in particular 1 MOhm. As a result, the losses can be significantly reduced compared to the prior art. In this case, a diode is coupled between the coupling point and the control input of the microcontroller, which serves for rectification.

In a particularly preferred embodiment, the microcontroller is designed such that it evaluates the peak value of the signal at its drive input. As a result, the noise immunity can be further increased. An average value measurement, on the other hand, would lead to a reduction of the signal-to-noise ratio.

Preferably, a predefinable threshold value is stored in the microcontroller, wherein the microcontroller is designed to classify a signal at its drive input as "high" when the peak value of the drive signal is above the predefinable threshold, and as "low" when the peak value of the drive signal below predetermined threshold is. In the microcontroller can be determined that a "high" leads to an activation of the at least fluorescent lamp and a "low" to activate the at least one LED.

Preferably, the predefinable threshold value stored in the microcontroller based on the peak value of the signal at the control input is between 15 and 25% of this peak value, in particular between 18 and 23%. Accordingly, in the case of an AC mains voltage which is customary in Germany with an amplitude of at most 255 units, the threshold value is preferably approximately 55 units. For other AC mains voltages, the threshold value can be adjusted accordingly.

Further preferably, the electronic ballast comprises a rectifier whose input has a first and a second input terminal, wherein the first input terminal is coupled to the second terminal, wherein the second input terminal is coupled to the first or the second or the third phase of a three-phase AC power supply, wherein the low potential at the output of the rectifier represents the reference potential of the electronic ballast. As a result of a suitably selected threshold value, as described above, the mains phase applied to the control input via the control device, that is to say in particular the motion detector, can be different from that at the mains input of the electronic ballast, which is then coupled to the rectifier. As a result, existing installations can be retrofitted to an energy-efficient system without much effort.

According to a particularly preferred embodiment, the control device is a motion detector.

Further preferred embodiments emerge from the subclaims.

Short description of the drawing (s)

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Show it:

1 a schematic representation of a known from the prior art evaluation of an electronic ballast;

2 a schematic representation of a constellation in which different lighting devices are switched via one and the same motion detector;

3 a schematic representation for explaining the problem by line capacitances in an electronic ballast according to the invention;

4 a schematic representation of the operation of a capacitive voltage divider in an electronic ballast according to the invention;

5 a schematic representation of the time course of the signal on the phase L1 to reference potential GND, the neutral conductor N to reference potential GND and the signal U _as at the control input of the microcontroller μC;

6 a schematic representation of an embodiment of an electronic ballast according to the invention;

7 a schematic representation of the time course of different network phases L1, L2, L3 in relation to the time course of the signal on the neutral conductor N; and

8th the time course of the signal U _as for the periods L = ON and N = ON, where within L = ON, the different. Curves are shown for SW = ON (curve a), SW = OFF without capacitive voltage divider (curve b), and SW = OFF with capacitive voltage divider (curve c).

Preferred embodiment of the invention

In the different figures, the same reference numerals are used for identical and equivalent components. These are therefore introduced only once for the sake of clarity.

2 shows a schematic representation of a problem, as it may occur in connection with the present invention. There are several lighting devices via one and the same motion detector 10 controlled. An example is an electronic ballast according to the invention 12 represented at the output of an LED and a discharge lamp FL1 are coupled. At the output of a second electronic ballast 13 a second discharge lamp FL2 is coupled. Finally, a light bulb 14 intended. In the ballast according to the invention, the ballast is coupled on the one hand with a phase L of a three-phase AC power supply, moreover with the neutral conductor N of the AC power supply. The switching output of the motion detector 10 is connected to a control input SW of the electronic ballast according to the invention 12 coupled. At the ballast 13 is the supply connection L with the switching output of the motion detector 10 coupled, while the neutral terminal N is coupled to the neutral conductor N. The lightbulb 14 Finally, between the switching output of the motion detector 10 and the neutral N coupled.

The problem with this constellation is that it is in phases in which the motion detector 10 is not switched on, or the phase L is "OFF" with the motion detector switched to an unwanted signal at the control input SW of a ballast according to the invention 12 can come as a result of, for example, a capacitive coupling between the L-terminal and the N-terminal in the electronic ballast 13 or simply by the fact that the light bulb 14 acts as an ohmic resistance and thus a signal from the neutral to the switching output of the motion detector 10 transfers.

3 shows that it is already without the in 2 presented constellation can come to problems of the signal at the control input SW and that as a result of sectional line capacitances Ck1, Ckn. The PE connection is intended for coupling with protective earth. Line capacities represent coupling capacities between a network phase, in this case L1, to the control line SL, which in this example is 25 m. The capacity pad is typically 100 pF / m and 120 pF / m maximum for a five-wire NYM cable with a diameter of 1.5 mm ² . The line capacitance Ck is the sum of the marked line capacitances Ck1 to Ckn. With switched motion detector 10 the line capacitance Ck is short-circuited, so that there are no problems at the control input SW of an electronic ballast according to the invention 12 comes.

In 3 an AC voltage supply AC is shown, whose neutral is coupled to the terminal N of an electronic ballast according to the invention and whose phase L1 on the one hand to the terminal L of an electronic ballast according to the invention and on the other hand with the motion detector 10 is coupled. The switching output of the motion detector 10 is with the control input SW of an electronic ballast according to the invention 12 coupled. According to this, the phases in which the motion detector is problematic are problematic 10 is switched on and the phase L1 is OFF or the phases in which the motion detector 10 is not switched on.

4 shows another illustration of the situation of 3 , where from the 4 Moreover, a measure to reduce the capacitive noise according to the present invention. Invention emerges. Like in the 3 an alternating voltage supply AC is provided, of which one phase is coupled to the terminal L of an electronic ballast according to the invention. The neutral conductor of the AC power supply AC is coupled to the terminal N of an electronic ballast according to the invention. Between the coupled to the terminal L phase of the AC power AC and the control input SW is as in 4 the motion detector 10 which is also in its non-conductive state to explain the principles of the present invention. Accordingly acts between the terminals L and SW of the electronic ballast according to the invention, the line capacitance C _k . Since this is actually distributed over several sections, it is in the representation of 4 dashed lines.

According to the invention, a capacitor C _{neu2 is} coupled between the connection SW and the connection N, which capacitance forms a capacitive voltage divider together with the line capacitance C _k . The goal is to keep the voltage U _{cneu2 dropping} across the capacitor C _neu2 by suitable dimensioning of the capacitor C _neu2 , if no control signal is present at the control input SW, ie the motion detector 10 is not switched on. The voltage drop across the line capacitance C _k is denoted by U _k . Preferably, the capacitance C _neu2 is chosen such that between the terminals L and SW approximately nine times the voltage drops as between the terminals SW and N.

As can be seen from the illustration, the voltage U _as dropped across the resistor R1 is fed to the drive input of the microprocessor μC using an ohmic voltage divider comprising the resistors R2 and R1. The diode D1 is used for rectification.

Before on the in 6 illustrated embodiment of an electronic ballast according to the invention 12 is to be discussed in more detail, is first on parts of the 5 Reference is made to Fig. 2, in which the time courses of some significant for the present invention voltages are shown schematically.

Curve a) first shows the time course of the voltage at the terminal L, that is in this case the phase L1, compared to ground, where Ground the reference potential of the electronic ballast 12 represents. Thus, this signal consists of a series of sinusoidal half-waves each interrupted by phases that last as long as a half-wave, with an amplitude of zero. Curve b) shows the time course of the voltage at terminal N opposite ground. As can be seen from the illustration, this course is also a sequence of sinusoidal half-waves which are interrupted by equal length phases with the amplitude zero. If one compares the signal according to curve a) and the signal according to curve b), then one finds that these are opposite-phase, that is, where curve a) has the amplitude zero, curve b) has a sinusoidal half-wave and vice versa.

Curve c) shows the time course of the voltage U _as at the control input of the microprocessor μC. On this curve is after discussion of in 5 illustrated embodiment of the present invention again reference.

At the in 6 illustrated embodiment of an electronic ballast according to the invention 12 is the line capacitance C _{k shown in} dashed lines between the exemplary selected phase L1 and the control input SW. With switched motion detector 10 the course of the signal at the control input SW corresponds to the curve a) of 5 ,

Therefore, when SW = ON, N is OFF. Thus, a signal is applied to the ohmic resistor R21 to a coupling point K, which in turn is connected via the diode D1 and the parallel circuit of the resistor R1 and a capacitor C3 to the reference potential. A coupled between the coupling point K and the reference potential capacitance C _neu1 is used to suppress interference due to burst pulses. The signal at the coupling point K is thus applied via the diode D1 to the drive input of the microprocessor μC.

As long as N is OFF, no signal is applied to the base of transistor Q1 via ohmic voltage divider R22, R3. The capacitor C2, which is connected in parallel with the ohmic resistor R3, serves to filter disturbances. Accordingly, the transistor Q1 blocks in this phase and does not affect the potential at the coupling point K.

In the phase where SW equals OFF, N equals ON. Characterized the transistor Q1 is turned on, whereby the potential at the coupling point K is pulled to reference potential. The voltage U _as at the control input of the microprocessor μC is therefore zero.

Particularly problematic is the phase in which the motion detector 10 is not switched to conduct, after which only a voltage due to the line capacitance C _k is present at the terminal SW. If now N is OFF, this could lead to an undesired voltage U _as at the control input of the microprocessor μC. _According to the invention, it is therefore provided to reduce the interference voltage caused by the line capacitance C _k to a non-critical voltage level at the input SW via a capacitor C _neu2 , which is coupled between the connection SW and the connection N. This ensures that, in this constellation, the voltage U _as at the control input of the microprocessor μC does not undesirably exceed a predefinable threshold value (TS) for activation of the fluorescent lamp FL.

The left half of the 6 shows that in the embodiment, an electronic ballast according to the invention has a terminal L for coupling to a phase and a terminal N for coupling to the neutral of a three-phase AC power supply. The terminals L and N, a rectifier is connected downstream, comprising the diodes D3, D4, D5 and D6. The parallel connection of a capacitor C4 and an ohmic resistor R _{LEVG is} coupled to the output of the rectifier, the ohmic resistor R _{LEVG representing} the load of the electronic ballast.

The curve c) of 5 shows the time course of the voltage U _as at the control input of the microprocessor μC when switched on motion detector 10 , It can be seen that a signal U _as is coupled to the microprocessor input μC only when N is OFF. This will be related to 2 addressed issue.

7 shows the time course of different phases L1, L2, L3 of a three-phase AC power AC based on the time course of the signal at the neutral. With reference to curve c) of 5 the peak value of the signal U _{as is} evaluated by the microprocessor .mu.C. If it is assumed that the maximum value of a half-wave would correspond to 255 units, a threshold TS, which is, for example, 55 units, can be provided in the microprocessor .mu.C. In the present case, the term "units" has been chosen since the actual voltage value is irrelevant; this can be adjusted by appropriate dimensioning, for example, the voltage divider involved as needed. Amplitudes above this threshold TS are regarded as "ON", that is to say logically "high", while signals below this threshold TS are regarded as "OFF", that is to say logically "low". The representation in the right half-wave of the curve c) reveals that even if not the phase L1 with the motion detector 10 is coupled, a reliable evaluation is possible. Even when using the phases L2 or L3 resulting in evaluation of the peak amplitude above the predetermined threshold TS, so that reliably a logical "high" can be distinguished from a logical "low".

In a preferred embodiment, the microcontroller .mu.C measures the amplitude of the signal _U.sub.as at its drive input every 400 .mu.s. In the case of the preferably selected threshold TS mentioned above, it is possible to use an electronic ballast according to the invention 12 use for mains voltages with a maximum amplitude between 140 and 400 ° V.

8th Finally, a schematic representation of the voltage U _as at the control input of the microprocessor μC for the cases SW = ON (curve a), SW = OFF and without the capacity C _neu2 (curve b), and SW = OFF with the capacity C _neu2 (curve c). It can be clearly seen that the contribution of the line capacitance could be significantly reduced using a capacitive voltage divider.

By the measures of the present invention, the length of the control line can be substantially five times. Applications that previously worked only with control cables up to 5 m can now be successfully implemented with control cables up to 25 m.

Claims (12)

An electronic ballast for operating at least one LED and / or at least one discharge lamp (FL), comprising: - a first terminal (L) for coupling to a phase (L1, L2, L3) of an AC power supply (AC); - a second terminal (N) for coupling to the neutral of the AC power supply (AC); A control input (SW) for coupling in a control signal of a control device ( 10 ), which in turn is coupled to a phase (L1, L2, L3) of the AC power supply (AC); A first output for coupling to the at least one LED; A second output for coupling to the at least one discharge lamp (FL); A first driver circuit for the at least one LED; A second drive circuit for the at least one discharge lamp (FL); - An evaluation device for evaluating the control signal at the control input (SW), wherein the evaluation device comprises a microcontroller (.mu.C) which is coupled to the first and the second driver circuit to activate them in response to the control signal, wherein the microcontroller (.mu.C) a Having drive input, which is coupled to the control input (SW); characterized in that a first capacitance (C _neu2 ) is coupled between the second terminal (N) and the control input (SW). Electronic ballast according to claim 1, characterized in that the evaluation device further comprises a masking device which is coupled between the control input (SW) and the control input of the microcontroller (.mu.C), wherein the masking device is designed, the control signal only during the periods to the control input of the microcontroller (μC) during which the signal at the second port (N) is zero. Electronic ballast according to claim 2, characterized in that the Ausblendvorrichtung comprises an electronic switch (Q1) having a control electrode, a reference electrode and a working electrode, wherein the control electrode is coupled to the second terminal (N), wherein the reference electrode is coupled to a reference potential , wherein the working electrode is coupled to a coupling point (K), which is coupled to the drive input of the microcontroller (.mu.C) on the one hand and the control input (SW) on the other hand. Electronic ballast according to one of the preceding claims, characterized in that a second capacitance (C _neu1 ) between the coupling point (K) and the reference potential is coupled. Electronic ballast according to one of claims 3 or 4, characterized in that between the control input (SW) and the coupling point (K) a first ohmic resistance (R21) and between the control input of the microcontroller (μC) and the reference potential, a second ohmic resistance ( R1) is coupled. Electronic ballast according to Claim 5, characterized in that a diode (D1) is coupled between the coupling point (K) and the control input of the microcontroller (μC). Electronic ballast according to one of the preceding claims, characterized in that the microcontroller (μC) is designed to evaluate the peak value of the signal (U _as ) at its drive input. Electronic ballast according to claim 7, characterized in that a predefinable threshold value (TS) is stored in the microcontroller (μC), the microcontroller (μC) being designed to classify a signal at its control input as "high" when the peak value of the control signal exceeds the predetermined threshold (TS), and as "low" when the peak value of the drive signal is below the predetermined threshold (TS). Electronic ballast according to claim 8, characterized in that in the microcontroller (.mu.C) stored specifiable. Threshold value (TS) based on the peak value of the signal (U _as ) at the control input (SW) is between 15 and 25% of this peak value, in particular between 18 and 23%. Electronic ballast according to one of the preceding claims, characterized in that the electronic ballast further comprises a rectifier (D3, D4, D5, D6) whose input has a first and a second input terminal, wherein the first input terminal to the second terminal (N) is coupled, wherein the second input terminal with the first (L1) or the second (L2) or the third phase (L3) of a three-phase. AC supply voltage (AC) is coupled, wherein the low potential at the output of the rectifier (D3, D4, D5, D6) represents the reference potential of the electronic ballast. Electronic ballast according to one of the preceding claims, characterized in that the input impedance of the control input (SW) is between 700 kOhm and 2 MOhm, in particular 1 MOhm. Electronic ballast according to one of the preceding claims, characterized in that the control device comprises a motion detector ( 10 ).

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